title: Prolonged bacterial culture to identify late periprosthetic joint infection: a promising strategy.
abstract: BACKGROUND
  The value of microbiological culture to diagnose late periprosthetic infection is limited, especially because standard methods may fail to detect biofilm-forming sessile or other fastidious bacteria. There is no agreement on the appropriate cultivation period, although this period is a crucial factor. This study was designed to assess the duration of culture that is necessary for reliable detection.
  
  
  METHODS
  Ten periprosthetic tissue specimens each were obtained during revision from 284 patients with suspected late hip or knee arthroplasty infection. Five samples were examined by microbiological culture over a 14-day period, and 5 were subjected to histologic analysis. To define infection, a pre-established algorithm was used; this included detection of indistinguishable organisms in >/=2 tissue samples or growth in 1 tissue sample and a positive result of histologic analysis (>5 neutrophils in at least 10 high-power fields). The time to detection of organisms was monitored.
  
  
  RESULTS
  Infection was diagnosed in 110 patients. After 7 days (the longest incubation period most frequently reported), the detection rate via culture was merely 73.6%. Organisms indicating infection were found for up to 13 days. "Early"-detected species (mostly staphylococci) emerged predominantly during the first week, whereas "late"-detected agents (mostly Propionibacterium species) were detected mainly during the second week. In both populations, an unequivocal correlation between the number of culture-positive tissue samples and positive results of histologic analysis was noted, which corroborated the evidence that true infections were detected over the entire cultivation period.
  
  
  CONCLUSIONS
  Prolonged microbiological culture for 2 weeks is promising because it yields signs of periprosthetic infection in a significant proportion of patients that would otherwise remain unidentified.
authors.affiliation: Ambulatory Healthcare Center, Labor Ludwigsburg, Ludwigsburg, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Schäfer
authors.forename: Bernd
authors.initials: B
authors.lastname: Fink
authors.forename: Dieter
authors.initials: D
authors.lastname: Sandow
authors.forename: Andreas
authors.initials: A
authors.lastname: Margull
authors.forename: Irina
authors.initials: I
authors.lastname: Berger
authors.forename: Lars
authors.initials: L
authors.lastname: Frommelt
mesh_terms: D000368:Aged; D001168:Arthritis / Q000175:diagnosis* / Q000382:microbiology / Q000473:pathology; D001419:Bacteria / Q000302:isolation & purification; D001424:Bacterial Infections / Q000175:diagnosis* / Q000382:microbiology / Q000473:pathology; D001431:Bacteriological Techniques; D005260:Female; D006615:Hip / Q000382:microbiology* / Q000473:pathology; D006801:Humans; D007717:Knee / Q000382:microbiology* / Q000473:pathology; D008297:Male; D016459:Prosthesis-Related Infections / Q000175:diagnosis* / Q000382:microbiology / Q000473:pathology; D013223:Statistics as Topic; D013997:Time Factors